Influence of the Main Characteristics of Low Weight Chitosan on the Growth of the Plant Pathogenic Fungus Botrytis сinerea

The effect of the main characteristics of low molecular weight chitosan obtained via enzymatic and chemical hydrolysis with a molecular mass (MM) of 2–100 kDa, a deacetylation degree (DD) of 60–98%, and a polydispersity (Mw/Mn) of 1.9–2.7 on the growth of Botrytis cinerea has been studied. The greatest inhibitory effect on the fungal germination process (a conidia germination index of less than 50%) was provided by chitosan samples with an MM of 2–13 kDa, a DD of 85–98%, and a polydispersity of 2–2.5. Among the most effective was chitosan with an MM of 13 kDa and a deacetylation degree 98%, which had a significant inhibitory effect on the growth of the fungal mycelium at concentration 0.938 mg/mL. This sample of chitosan and its complex with copper ions (75 ppm) significantly suppressed fungal metabolic activity (up to 20 and 10%, respectively), which indicates their high potential as antifungal agents for the development of fungicides.